**4. Conclusions**

All available technological approaches can be divided into three groups following the classification proposed by the authors of the types of adaptive materials and coatings (AMCs) for tool purposes, showing the ability to adapt to external negative conditions:


The complex analytical studies carried out in this work allow us to judge the current directions of work of the leading research teams in the development and application of AMCs, aimed at maintaining the working capacity of the cutting tool for a longer time. The developed technological approaches are compared with the options of tool wear in practice under various operating conditions, and the areas of their practical application are determined.

It can be concluded that the most extensive group is AMCs from the point of view of implementation options, scale, and depth of research. They can provide structural self-organization of the surface layer of the cutting tool due to the formation of secondary structures in contact with the environment and the workpiece being machined under the conditions of heat and power loads acting during cutting. The data presented in the paper illustrate how a properly designed surface layer can effectively adapt to external negative conditions.

Based on the experimental results of the authors of the work, composite powder high speed steels (CPHSSs) were proposed and studied as a typical example of a material with adaptive abilities under operational loads, the components of which are refractory compounds such as TiC, TiCN, and Al2O3. It was instrumentally confirmed that the thin surface films formed when cutting based on secondary phases, such as thermally stable compounds of titanium with oxygen and nitrogen, significantly reduce the frictional interaction intensity and redistribute the thermal fields in the cutting zone at the tool–chip interface section of the tool cutting wedge. The established changes in the surface layer provide a twofold increase in tool life during milling, which was confirmed in laboratory conditions and improve the workpiece's surface quality.

**Author Contributions:** Conceptualization, S.N.G.; methodology, M.S.M. and M.A.V.; validation, S.V.F. and A.A.O.; formal analysis, Y.A.M., A.A.O., and V.D.G.; investigation, S.V.F., M.S.M., and M.A.V.; resources, Y.A.M. and V.D.G.; data curation, S.V.F. and A.A.O.; writing—original draft preparation, M.S.M.; writing—review and editing, M.A.V.; visualization, Y.A.M. and M.A.V.; supervision, V.D.G. and S.N.G.; project administration, S.N.G. All authors have read and agreed to the published version of the manuscript.

**Funding:** The study was supported by a grant of the Russian Science Foundation (project No. 21- 79-30058). The work was carried out on the equipment of the Center of Collective Use of MSUT "STANKIN".

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Data are available in a publicly accessible repository.

**Acknowledgments:** The authors are grateful to Pavel Podrabinnik for his help in timely obtaining the most relevant data regarding the study of samples.

**Conflicts of Interest:** The authors declare no conflict of interest.

#### **References**

